diff --git a/chrome/content/zotero/xpcom/sync/syncAPIClient.js b/chrome/content/zotero/xpcom/sync/syncAPIClient.js
index 5538dc9526..1a9a822715 100644
--- a/chrome/content/zotero/xpcom/sync/syncAPIClient.js
+++ b/chrome/content/zotero/xpcom/sync/syncAPIClient.js
@@ -35,6 +35,7 @@ Zotero.Sync.APIClient = function (options) {
 	this.baseURL = options.baseURL;
 	this.apiVersion = options.apiVersion;
 	this.apiKey = options.apiKey;
+	this.schemaVersion = options.schemaVersion || Zotero.Schema.globalSchemaVersion;
 	this.caller = options.caller;
 	this.debugUploadPolicy = Zotero.Prefs.get('sync.debugUploadPolicy');
 	this.cancellerReceiver = options.cancellerReceiver;
@@ -616,6 +617,7 @@ Zotero.Sync.APIClient.prototype = {
 		if (this.apiKey) {
 			newHeaders["Zotero-API-Key"] = this.apiKey;
 		}
+		newHeaders["Zotero-Schema-Version"] = this.schemaVersion;
 		return newHeaders;
 	},
 	
diff --git a/chrome/content/zotero/xpcom/sync/syncRunner.js b/chrome/content/zotero/xpcom/sync/syncRunner.js
index 61d97e85b6..046f9a9f4b 100644
--- a/chrome/content/zotero/xpcom/sync/syncRunner.js
+++ b/chrome/content/zotero/xpcom/sync/syncRunner.js
@@ -95,6 +95,7 @@ Zotero.Sync.Runner_Module = function (options = {}) {
 		return new Zotero.Sync.APIClient({
 			baseURL: this.baseURL,
 			apiVersion: this.apiVersion,
+			schemaVersion: this.globalSchemaVersion,
 			apiKey: options.apiKey,
 			caller: this.caller,
 			cancellerReceiver: _cancellerReceiver,
diff --git a/test/tests/syncAPIClientTest.js b/test/tests/syncAPIClientTest.js
index 35867158d5..481a5d9951 100644
--- a/test/tests/syncAPIClientTest.js
+++ b/test/tests/syncAPIClientTest.js
@@ -43,6 +43,31 @@ describe("Zotero.Sync.APIClient", function () {
 		Zotero.HTTP.mock = null;
 	})
 	
+	
+	describe("#makeRequest()", function () {
+		after(function () {
+			sinon.restore();
+		});
+		
+		it("should send Zotero-Schema-Version", async function () {
+			server.respond(function (req) {
+				if (req.method == "GET" && req.url == baseURL + "test-schema-version") {
+					assert.propertyVal(
+						req.requestHeaders,
+						'Zotero-Schema-Version',
+						Zotero.Schema.globalSchemaVersion.toString()
+					);
+					
+					req.respond(200, {}, "");
+				}
+			});
+			var spy = sinon.spy(Zotero.HTTP, "request");
+			await client.makeRequest("GET", baseURL + "test-schema-version");
+			assert.isTrue(spy.calledOnce);
+		});
+	});
+	
+	
 	describe("#getGroups()", function () {
 		it("should automatically fetch multiple pages of results", function* () {
 			function groupJSON(groupID) {